Fluid heat exchange apparatus



Sept. 9, 194-1. E TQLLQW 2,255,233

FLUID HEAT EXCHANGE APPARATUS Filed April 22, 1938 2 Sheets-Sheet l INVENTOR. fiederick Sidney YH/ow- AORNEY.

p 1941- F. s. TOLLOW 2,255,233

FLUID HEAT EXCHANGE APPARATUS Filed April 22, 1938 2' Sheets-Sheet 2 ATTORNEY.

Patented Sept. 9, 1941 rarest are FLUID HEAT EXGHANGE APPARATUS Frederick Sidney Tollow, Wh'yteleafe, England,

assignor to The Babcock & Wilcox Company, Newark, N. 5., a corporation of New Jersey ApplieationApril 22, 1938, SerialNo. 203,556

In- Great Britain June 11, 1937 (Cl. 122 l8ii) 4 Claims.

perheater and the bafi'les for controlling the gas how be effectively disposed relative to the remainder of the boiler. When the superheater includes a plurality of sections, it is also important to be able to effect a proper distribution of steam fiow through the tubes of the respective sections.

An object of the invention is to provide a vapor generator accomplishing the above indicated results and also maintaining a relatively high rate of gas flow over the superheating surfaces in order that adequate superheat may be attained at low loads, using a convection superheater of reasonable size; A further object of the invention is to provide a combined vapor generator and multiple-section superheater installation which effectively utilizes economizer surfaces at all loads.

One form of the invention is represented by a vapor generator which comprises an economizer, separate superheaters or steam heaters, and a bypass for the gas pass in which one of the superheaters is located. The invention also presents means for varying the proportion of the total gas flow over the superheater surfaces.

The arrangement of the economizer is such that the complete economizer is subjected to the flow of all of the furnace gases regardless of the proportion of the total gas flow passing over the bypassed superheater or steam heater surface.

The invention also relates to a vapor generator including a casing which houses a superheater and vapor generating tubes, the space within the casing beyond the generating tubes, and in the direction of gas flow, being divided into a plurality of series-connected gas passes of reduced cross section. One of these gas passes always has the entire gas flow passing through it, and in this pass is arranged one of the superheater sections. In another of the gas passes there is located another section of the superheater around which the gases may be bypassed to an adjustable extent.

The invention will be described with reference to the accompanying drawings, in which:

Fig. 1 is a sectional side elevation'of the illustrative boiler provided with an air heater;

Fig. 2 is a front elevation of the steam generator with the left-hand half of the boiler shown in vertical section; and

Fig. 3 is a sectionalside elevation of a modifi-w cation of the illustrative installation.

The steam generator illustrated in' the drawings includes the bank of steam generating tubes l disposed across the gas outlet of the furnace 2.

These tubes are associated with sectional head-' ers 3-and 4 which are connected with the drum 8 by the downcomers 9, the risers 5, and circu lators l. The risers and circulators are in communication by reason of their connection wit the header 6.

The walls of the furnace 2 include water tubes iil connecting upper headers l l to lower headers l2 and suitably connected into the circulatory system of the steam generator, the tubes being suitably covered, as, for example, by Bailey blocks. 7

The steam generator is provided with structural-supporting members including the uprights l3, and the furnace and the gas space above the furnace are provided with a suitable casing the elements of which adjacent the headers 3 and adjacent the space above the furnace at the front of the steam generator are in the form of the removable panels It.

The superheater space above the'stearn generating tubes l is divided into two upflow passes i5 and I6, and a connecting downfiow pass ll.

One section, E8, of the superheater. is disposed in the gas pass l5 and a second superheater section i9 is disposed within the gas pass 6. The latter superheater section is adapted to be bypassed to an adjustable extent, as described below. Arranged beyond the gas pass IE and the superheater section !9 therein is a gas pass it which is subjected to the entire gas flow regardless of the extent of the bypassing of the superheater section it. An economizer 2! is arranged within the gas pass 2i The gas passes 15 and t? are separated by the baffle 22, a similar baffle 23 separating the gas passes it and ll. The tubes 2d and 25 supporting and forming parts of these bafiies are connected at their lower ends to the headers 4 andat their upper ends to a header 2% which is in communication with the steam space of the drum 8 by means of the tubes 27. In forming the baflles' the spaces between the tubes 25 and 25 may be closed, at the locations of the bailies, with suitable refractory material, andthe baffle 23, near the upper part thereof, is provided with bypass apertures 28 through which gases may be allowed to flow into the space 29, thereby bypassing the superheater section I9.

The superheater section [8 is always subjected to the entire gas fiow, and that portion of the gases which is not bypassed through the apertures 28 flows downwardly through the bypass ll, between the lower portions of the tubes 25, and then upwardly through the gas pass I6 in the upper part of which it joins the bypassed gases to form a common stream which then passes between the upper portions of the downcomers 9 and. through an outlet 30 leading to the economizer 2|. 7 a

The primary superheater section, or primary superheater, I8, consists of a bank of tubes'connected by return bends disposed in Vertical planes. These tubes are arranged between and supported by the risers and the bafile tubes 24, and the lower ends of these superheater tubes are connected to the superheater outlet header 3! through which this section of the superheater is drainable.

The secondary section of the superheater, or secondary superheater, i9, is similarly arranged between the tubes 25 and the downcomers 9, the lower ends of the tubes of this section being connected with the superheater inlet header 32 through which this section of the superheater may be drained.

It will be observed that the tubes of the superheater section I9 are connected in series with the respective tubes of the superheater section l8, these connections being eifected by the tubes 33 and the connectors 34. The header 32 is suitably connected with the steam space of the drum 8, the arrangement being such that the steam flows from the drum through the secondary superheater section l9 and then through the primary superheater section 18, in counter-flow with reference to the gases.

Steam is admitted to the header 32 by connecting the steam space of the drum to a plurality of points in the length of the header, so that a substantially uniform distribution of steam is established in the tubes of the secondary superheater section [9, and since the tubes of the primary superheater section l8 are severally connected in series with the tubes of the section l9 proper distribution of steam flow is also obtained in the primary superheater section.

The gases from the economizer gas pass 20 pass by way of a duct 31 to an air heater 40 disposed below the economizer. After passing through the air heater the gases are discharged from the duct 4|. A forced draft fan 35 forces air through the air heater and then through the ducts 36 to the furnace 2.

For the purpose of controlling superheat, gas flow regulators 38 are provided for the apertures 28 in the baflie 23. They are preferably hinged at 39 along their upper edges and are adapted to open inwardly into the space 29. With this arrangement of elements the devices for operating the regulators, and the hinges for the latter, are conveniently arranged at positions substantially outside of the path of the gases.

Superheat may be maintained at a constant Value while the boiler is operating over a wide range of capacities, by operating the regulators 38 in response to variations in certain pertinent factors. This may be accomplished by control mechanism which includes temperature responsive elements functioning in conjunction with other means responsive to steam flow.

In the embodiment of the invention illustrated in Fig. 3 of the drawings, the arrangement of the gas passes 59, 52, and 54 is similar to the arrangement of passes in the Fig. 1 steam generator and these gas passes are similarly arranged above a bank of steam generating tubes 56 corresponding to the bank of steam generating tubes l in Fig. 1. However, in the up-pass 54, an economizer 58 is provided. This economizer includes the headers 69 and 62 connected by return bend tubes which extend across the gas pass. In the up-pass 50 the superheater B4 is arranged. This includes the headers 66 and 68 connected by an arrangement of tubes similar to the tubes I in the superheater I8 of the Fig. 1 embodiment. Beyond the economizer, and above it, is the flue 10 through which the gases may pass to an air heater.

While the invention has been described with reference to the particular embodiment shown in the drawings, it is to be appreciated that it is not limited to all of the details thereof. The

invention is rather of a scope commensurate with the scope of the subjoined claims.

What is claimed is:

1. A vapor generator comprising, in combination, vapor generating tubes, a superheater, a casing wherein the space beyond the vapor generating tubes in the direction of gas flow is divided into three side-by-side and series-connected passes of reduced cross section, the first of said passes being arranged to always be sublect to the total gas flow from the furnace and having one separate section of the superheater therein, another separate section of the superheater being arranged in the third of the gas passes, means forming a gas outlet at the discharge end of the last of said passes, bafiles or walls separating said passes, a gas flow regulator associated with an opening in the wall between the second and third of said passes and adjacent the gas entrance to the second of said passes, said outlet being disposed on the downstream side of said other separate superheater section relative to the flow of gases over that superheater section, said opening establishing communication between the upstream and downstream sides of the second superheater section, and means connecting said superheater sections for series steam flow therethrough.

2. A vapor generator comprising, in combination, a furnace, a bank of vapor generating tubes beyond the furnace relative to the direction of gas flow, a superheater, and a casing affording a space for the superheater beyond the vapor generating tubes, baflles or walls whereby the said space is divided into first and second upfiow passes and an intermediate downflow pass in series with the upfiow passes, means forming a furnace gas outlet at the discharge end of the second up-fiow pass, the superheater having one separate section thereof disposed in the first upflow pass, a second separate section disposed in the second upiiow pass; and a gas flow regulator operating across an opening in the wall dividing the second upflow pass from the intermediate pass to cause furnace gases to by-pass the intermediate pass and the second superheater section, the path of gas flow from the dampered opening to a position beyond the second superheater section having a pressure drop less than the pressure drop of the gas path through (or over) the second superheater section.

3. A Vapor generator comprising, in combination, vapor generating tubes, a superheater, a casing wherein the space beyond the vapor generating tubes in the direction of gas flow is divided into three successive and side by side gas passes of reduced cross-section connected for gas flow in series therethrough, means forming a gas outlet at the discharge end of the last of said passes, one of said passes being arranged to always be subject to the total gas flow from the furnace and having superheater tubes disposed transversely of gas flow therein, a second superheater section disposed transversely of gas flow in one of the last two gas passes, and a gas flow regulator disposed across an opening between the second and third passes to cause a controlled proportion of the gases to bypass said second superheater section and the last two of said gas passes, said regulator being so arranged between the exit of the first pass and said gas outlet as to afford direct gas flow therebetween during said by-passing, the path of gas flow from the dampered opening to a position beyond the second superheater section having a pressure drop less than the pressure drop of the gas path through (or over) the second superheater section.

4. In a superheater and steam generator installation, steam generating tubes, means forming at least three successive and parallel gas passes connected in series as to gas flow, a superheater section in the first of said passes, a second superheater section in the third of said passes, said means including bailles or walls dividing said passes, means forming a gas outlet at the discharge end of said last gas pass, means connecting the superheater sections in series as to steam flow, and a gas flow regulator operating across an opening in the wall between the second and third gas passes to control superheat by permitting a variable proportion of the furnace gases to by-pass the second superheater section and pass directly from the exit of the first of said passes to said gas outlet, the path of gas flow from the dampered opening to a position beyond the second superheater section having a pressure drop less than the pressure drop of the gas path through (or over) the second superheater section.

FREDERICK SIDNEY TOLLOW. 

